Move edge along normal of other face?
edge slide CTRL E does not work in this usage case, because of the topology. besides the solution provided by Gandalf3, here is a somewhat more complicated alternative which i just keep here as a sidenote:

Select the Face along which you want to move the edge:


Set the 3D Manipulator widget's Transform orientatin to &quot;View&quot;

View -&gt; Align View -&gt; Align View to Active -&gt; Top


Select Edge Select Mode

Select the edges that you want to slide


now you can slide the edges upwards and be sure they slide along the face that you selected in 1. above